A nerd needs a project because a nerd builds stuff. All the time. Those lulls in the conversation over dinner? That's the nerd working on his project in his head.
Rands in Repose has a fantastic Nerd Handbook, and honestly, I can’t imagine a more succinct and complete guide to the nerd in your life.
Humor is an intellectual puzzle, "How can this particular set of esoteric trivia be constructed to maximize hilarity as quickly as possible?" Your nerd listens hard to recognize humor potential and when he hears it, he furiously scours his mind to find relevant content from his experience so he can get the funny out as quickly as possible.
Seriously, go read it, because it’s perfect.